The present invention relates to a rear suspension controller for a vehicle, particularly to a rear suspension controller which is effective against a sporadic shock caused by a protrusion or sinking of a road surface on which an automobile is running.
Conventionally, the spring constant or damping force of each of various kinds of suspension components provided between the body and wheels of a vehicle is altered under control depending on the condition of the road surface or the running condition of the vehicle to prevent the vehicle from being shocked or vibrated or keep the controllablity and the stability of the vehicle good. For example, altering the spring constant of the air spring of a suspension depending on the condition of the road surface was proposed in the published unexamined Japanese patent applications Nos. Sho-59-23712 and Sho-59-26638. In such control, the characteristic of the suspension is altered when the running of the vehicle on a rough part of the road surface is detected by a vehicle height sensor or when it is found out by a brake sensor or an accelerator sensor that the front of the vehicle has gone up or down, to keep the controllability and the stability of the vehicle good during its running on the rough part of the road surface or to prevent the front of the vehicle from going up or down further. In the above-mentioned conventional control, only when a continuous large turbulence is detected by the vehicle height sensor, the vehicle is judged to be running on the rough part of the road surface, so that the spring constants of the suspensions for all the wheels of the vehicle are increased to produce a desired effect. However, when the vehicle passes over such sporadic protrusion or sinking of the road surface as a joint of the road patches, the vehicle receives only a sporadic shock and then resumes running on a flat part of the road surface, so that the characteristic of each suspension is not altered. For that reason, in running over such sporadic protrusion or sinking, the passengers of the vehicle are not protected from an unpleasant shock, so that the feel of ride of the vehicle is deteriorated.